The present invention relates to a method for sharing channels between the sectors of a base station and between Frequency Assignments (FAs) in Code Division Multiple Access (CDMA) system. More particularly, the present invention relates to a method for the base station to share channels from adjacent cellular base stations or between frequency assignments therebetween, which helps to reduce numbers of channel cards used in the base station.
A cellular mobile telecommunication system makes it possible for more subscribers to communicate with each other by improving the efficiency in the amount of traffic capacity that can be carried in allocated radio spectrum bands. As a demand for cellular service grows, operator of such system attempts to make maximum effective use of the available radio frequency bandwidth in order to accommodate the service demand.
A cell division technology is widely used to improve the efficiency in frequency reuse. One of the known cell division technologies is a sectorization. In such a method, a cell is generally divided into three equal parts (xcex1, xcex2, and xcex3 sector) by spacing three 120 degrees antennas. Presently, the CDMA system assigns a group of traffic channels to each sector in the base station, and one of these traffic channels of the corresponding sector is assigned to the traffic in the event that a subscriber is accessing the system to establish a communication link. However, as the number of the subscribers grow rapidly in a given sector, there is a strong interest to enhance the system capacity for a given grade of service. This can be achieved by using surplus traffic channels in other sectors that are not being used. Some schemes have been developed to share the channels between sectors to accommodate user communication overloads that occur within a particular cellular region.
One of the prior arts used for sharing channels of the CDMA system involves reserving a group of traffic channels for borrowing during regional overloads, where it has been saturated. If the traffic overload occurs in a specific sector, one of the reserved traffic channels is borrowed by the sector where the traffic overload occurred. Accordingly, such method for sharing channels allows the xcex1, xcex2, xcex3 sectors to share/borrow from a group of reserved traffic channels, indiscriminately.
Another known art involves sharing of unassigned frequency bands to provide communications service during the traffic overloads. As the number of subscribers grows the sector accommodates more subscribers by using frequency assignment process, which attempts to avoid assigning the same frequency to each mobile station. If the number of subscribers is added, the sector provides the new mobile station with a new frequency assignment that is available for use. Each FA has its own codes, different from each other, serving to provide various traffic channels. The systems then share the unassigned frequency bands to accommodate the overload.
As discussed in the above, there is provided in the prior arts for sharing channels only between the sectors in the CDMA system. However, so far there exists no method for sharing channels between FA (namely 1FA, 2FA, 3FA, etc) for reducing the numbers of packaged channel cards in a base station.
Since the demand for channels to serve users of cellular communication system is expected to grow rapidly in the near future, there is a strong interest to develop techniques that would enhance the system utility and simplicity, and lighter and less complex system.
The object of present invention is to improve the simplicity, complexity, and weight of the system, through reducing the numbers of packaged channel cards required in the system by sharing channels between frequency assignments and between sectors.
Other objects and advantages of the present invention will become apparent with reference to the following detailed description and the attached drawings.
One of the preferred embodiment of a channel-sharing method between base station sectors and frequency assignments (FAs) in code division multiple access (CDMA) system, the method comprising the steps of:
setting traffic channels to accommodate the subscribers"" traffic occurred in the base station;
determining whether the set channels are to be shared between only FAs after setting the traffic channels;
in case the set channels are shared only between FAs, obtaining Z the number of channel cards by       XY    W    ,
xe2x80x83wherein X is the sum of the set traffic channels and the overhead channels, Y is the number of FAs and W is the number of total channels per each channel card;
setting the set traffic channels to the channel cards and sharing channels using the set channel card only between FAs;
in case sectors and channels are shared between the FAs and between the sectors, obtaining Z, by calculating       kXY    W    ,
xe2x80x83wherein k is the number of sectors; and setting the traffic channels to the channel cards and sharing channels using the set channel card between the sectors and FAs.
And it is preferable that in case channels are shared only between FAs, Z is obtained by calculating   k  xc3x97  CEILING  ⁢      xe2x80x83    ⁢            FUNCTION      ⁡              (                  XY          W                )              .  
It is preferable that in case channels are shared between sectors and between FAs, Z is obtained by calculating   CELILNG  ⁢      xe2x80x83    ⁢            FUNCTION      ⁡              (                  kXY          W                )              .  
Another preferred embodiment of a channel-sharing method between base station sectors and frequency assignments in code division multiple access (CDMA) system, the base station having a plurality of sectors and operating a plurality of FAs to provide mobile communication services by sharing the channels between the sectors during the traffic overlaods, and that the number of channel cards (Z) is obtained by calculating       k    xc3x97    CEILING    ⁢          xe2x80x83        ⁢          FUNCTION      ⁡              (                  XY          W                )              ,
where X represents the sum of the set traffic channels and the overhead channels, Y represents the number of FAs, W represents the number of total channels per each channel card and k is the number of sectors.
Other preferred embodiment of a channel-sharing method between base station sectors and frequency assignments (FAs) in code division multiple access (CDMA) system, the base station having a plurality of sectors and operating a plurality of FAs to provide mobile communication service by sharing the channels between the sectors and between the plurality of FAs during the traffic overloads, and the number of channel cards (Z) is obtained by calculating       CEILING    ⁢          xe2x80x83        ⁢          FUNCTION      ⁡              (                  kXY          W                )              ,
where X represents the sum of the set traffic channels and the overhead channels, Y represents the number of FAs, W represents the number of total channels per each channel card and k is the number of sectors.